I have a homosexual female friend.
She made some excellent points when discussing this a few months back.
She grew up when being bay was wrong. Married had children and divorced when that became ok. Started same set relationship when that became for acceptable.
She dresses in jeans/ combat shorts, polo t shirts and hoodies, trainers. She has shirt hair. Never dresses in dresses or skirts and smart to her is trousers and shirt, blazer if cold.
Like me she's very liberal but also thinks we over discuss these things nowadays which makes kids want to experiment.
She also said during our deep conversation about life that evening she is glad she's an adult in the 21st century. That as a gay woman who dresses the way she does (btw I dress equally the same but I'm also a dress person - dependent on what way the winds blowing!) she thinks as a child growing up in this current climate and being "out" she'd have had people trying to shoehorn her into some box and put a label on it.
But as she says she's just a homosexual woman who dresses how she's comfortable. She'd never considered it to be masculine or questioned her sexual assignment or gender - it's just her sexual preferences are same sex.
I agree with above posters that I'd approach it with asking her what her choices mean to her. Ask her to define what she means. She needs to know she doesn't have to label herself to define who she is. Who she is is enough without needing to box and label it.
I do worry for teens nowadays. They seem to think just being Anne, Jane, Thomas or Matt isn't enough. They have to describe themselves much more definitively .